Our asthma research program involves both exposure assessment and prevention components, and focuses on the relationship between exposure to common indoor allergens and asthma prevalence and morbidity. We have worked with investigators at the CDC/NCHS to implement the allergen and asthma component of National Health and Nutrition Examination Survey (NHANES) 2005-2006. We collected bedroom dust, measured serum total and allergen-specific IgE and assessed asthma and allergy prevalence and morbidity in approximately 9000 individuals in the U.S. Analysis of this large data set will allow us to 1) estimate nationwide prevalence of indoor allergen and endotoxin exposures, 2) estimate nationwide prevalence of allergic sensitization to indoor, outdoor and food allergens, 3) estimate nationwide prevalence of allergic diseases, including asthma, and 4) investigate the complex relationships between allergen and endotoxin exposures, allergic sensitization and allergic diseases. NHANES 2005-2006 not only tested a greater number of allergens across a wider age range than prior studies, but also provided quantitative information on the extent of allergic sensitization and exposures to indoor allergens and endotoxin. The NHANES 2005-2006 data demonstrated that a large portion of the US population is sensitized to indoor, outdoor, and food allergens. Sensitization showed clustering patterns that might have largely reflected biological cross-reactivity. Although the overall prevalence of sensitization did not vary across census regions, except in early life, the the prevalence of sensitization to individual allergens and allergen types showed regional differences. Positive specific IgE (sIgE) responses (i.e., sensitization) and increased sIgE levels were most consistently associated with age, sex, race/ethnicity, census region, and reported pet avoidance measures. Using the data from this large, nationally representative sample of the U.S. population, we assessed whether phthalate metabolites were associated with allergic symptoms and sensitization, since environmental exposure to phthalates, particularly high molecular weight (HMW) phthalates, is suspected to contribute to allergy. We found that HMW phthalates, especially mono-benzyl phthalate (MBzP), were positively associated with allergic symptoms and sensitization in adults, but there was no strong evidence for phthalates and allergy in children aged 6-17 years. This study is the largest to date to evaluate the association of phthalates on allergic sensitization and symptoms in both adults and children. To investigate the relationship between ambient air pollution and allergic sensitization, we linked air pollution concentrations from U.S. Environmental Protection Agency Air Quality Systems (AQS) monitored data and community Multiscale Air Quality (CMAQ) model data to the NHANES 2005-2006 data set. Our results suggested that increased levels of ambient nitrogen dioxide (NO2) were associated with increased prevalence of allergic sensitization. This study was the first to assess the relationship between air pollution and allergic sensitization in a nationally representative sample of the U.S. population. Although dyslipidemia has been associated with leukocytosis, the relationship between serum cholesterol and other hematopoietic lineages is poorly defined. As we examined the relationship between serum cholesterol and circulating erythrocyte/platelet indices in NHANES 2005-2006 data, we found that serum non-high density lipoprotein-cholesterol (non-HDL-C) is directly related to abundance measures of circulating erythrocytes and platelets in the U.S. population, whereas HDL-C is directly related to mean corpuscular volume (MCV). Given that elevated erythrocytes, platelets, and hypercholesterolemia are all established risk factors for coronary disease and that hypercholesterolemia impairs erythrocyte deformability and activates platelets, our findings suggest an important need for characterizing possible mechanisms by which serum cholesterol and population kinetics of erythrocytes and platelets may impact one another. Many exposures potentially linked to respiratory disease in farmers are also important for general population. Understanding risks among farmers and how these differ from the population at large may shed light on environmental contributors to respiratory disease in the population as a whole. We compared the respiratory health of a U.S. farming population with that of the general population (NHANES 2005-2006). Our results suggest that farmers and their spouses have lower risk for adult-onset respiratory diseases compared with the general population, and potentially higher respiratory irritation as evidenced by increased respiratory symptoms. Since the NHANES data set allows for the investigation of many interesting relationships, we continue to investigate the complex relationships between allergen exposure, allergic sensitization, and disease in more detail. In addition to providing data on these relationships, the NHANES 2005-2006 will establish a second point-in-time estimate for evaluating allergen and endotoxin exposure trends in U.S. homes, first being established in the National Survey of Lead and Allergens in Housing, which we completed in collaboration with the Department of Housing and Urban Development.